The present invention relates to an internal combustion engine with dual induction system including a primary induction system to direct a first fluid charge into a cylinder to swirl therein under all operating conditions of the engine and a secondary induction system to direct a second fluid charge into the cylinder in such a direction as to impede and reduce the swirling motion of the first fluid charge issuing from said primary induction system under predetermined operating conditions of the engine, and maintain the volumetric efficiency of the engine at a high level under these predetermined operating conditions.
For the purpose of purification of exhaust gases resulting from combustion within an internal combustion engine, an air fuel mixture having a great air fuel ratio is burnt during the combustion or an air fuel mixture is burnt at an increased exhaust gas recirculation rate (EGR rate) during the combustion. Since flame propagation speed decreases as the air fuel ratio is increased or EGR rate is increased, it is necessary and known to increase the swirl rate within a combustion chamber of the engine to such a degree as to obtain fast burn combustion.
Various fuel mixture introductions have been employed to produce fuel mixture swirling within a cylinder, for example, complicated intake port shapes; or shrouded intake valves. If such a complicated induction arrangement is employed, the volumetric efficiency of the engine is impaired at high loads and as a result the power output under full or high load conditions drops.
Dual induction systems for internal combustion engines including dual passages and ports for the combustion chambers of internal combustion engines are known in the art. These dual induction systems include a small primary passage communicating with a primary side of a carburetor and with a small intake valve in a combustion chamber and a large secondary passage communicating with a secondary side of the carburetor and with a large intake valve in the combustion chamber. In these systems an air fuel mixture for engine operation at low and intermediate loads is supplied to the combustion chamber from the primary side of the carburetor through the small primary passages and a second air fuel mixture is supplied to the combustion chambers from the secondary side of the carburetor, too, when the internal combustion engine is operating under high load conditions, such as those that occur during peak acceleration periods and at wide open throttle.
These dual induction systems have several advantages over the conventional single induction systems currently used in internal combustion engines that employ a single induction passage leading from a carburetor to an intake valve located in a combustion chamber. At low and intermediate loads the air flow through the primary induction passages has a velocity sufficient to fully mix the fuel with the air. This action results in more complete burning of the fuel in each combustion of the internal combustion engine, thereby resulting in better engine operation and a reduction in the unburnt hydrocarbons and carbon monoxide emitted by the internal combustion engine.
With these dual induction systems, if the air fuel ratio is increased sufficiently to obtain lean burn combustion or the exhaust gas recirculation rate (EGR rate) is increased sufficiently to obtain a marked reduction in nitrogen oxides emitted by the internal combustion engine, the flame propagation speed within each combustion chamber of the internal combustion engine drops when the engine is operating at low crankshaft speeds under light load conditions, thereby resulting in poor engine operation.